The skin is made up of three distinct layers. The top layer is called the epidermis. The epidermis is translucent. That is, it allows light to pass partially through it, rather as frosted glass does. The epidermis does not contain any blood vessels but gets its oxygen and nutrients from the deeper layers of the skin. At the bottom of the epidermis is a very thin membrane called the basement membrane which attaches the epidermis firmly, but not rigidly, to the underlying layer. The second layer lies deeper and is called the dermis. It contains blood vessels, nerves, hair roots and sweat glands. Below the dermis lies a layer of fat, the subcutaneous fat. The depth of this layer differs from one person to another. It contains larger blood vessels and nerves, and is made up of clumps of fat-filled cells called adipose cells.
The subcutaneous fat lies on the muscles and bones, to which the whole skin structure is attached by connective tissue. The attachment is quite loose, so the skin can move fairly freely. If the subcutaneous tissues fill up with too much fat, the areas of attachment become more obvious and the skin cannot move as easily. This is what gives rise to the notorious cellulite.
The junction between the epidermis and the dermis is not straight but undulates like rolling hills, more markedly so in some areas of the body than others. A series of finger-like structures called rete pegs project up from the dermis, and similar structures project down from the epidermis. These projections increase the area of contact between the layers of skin, and help to prevent the epidermis from being sheared off.
Excess adipose tissue is responsible for such medical problems as obesity, cellulites, loose skin, and wrinkles. By reducing the size of fat cells, the appearance of the outer layer of the skin can be improved. The reduction of adipose tissue in the sub-dermal layer often provides the following medical and cosmetic solutions: weight reduction, cellulite reduction, loose skin reduction, deep wrinkle reduction and body re-contouring. Reduction of the fat content may also cause skin tightening. Wrinkles are created in skin due to the breakage of collagen fibers and to the penetration of fat into the dermal layer of the skin.
Most existing wrinkle treatment methods target the collagen but do not have a significant effect on deep wrinkles. Radio frequency (RF) energy has been actively used for the treatment of epidermal and dermal layers of the skin. For example U.S. Pat. No. 6,749,626 describes the use of RF energy for collagen formation in the dermis. U.S. Pat. No. 6,241,753 describes a method for collagen scar formation. U.S. Pat. Nos. 6,470,216, 6,438,424, 6,430,446 and 6,461,378 disclose methods and devices for destroying the collagen matrix using RF, cooling and a special electrode structure that smoothes the skin surface. U.S. Pat. Nos. 6,453,202, 6,405,090, 6,381,497, 6,311,090, 5,871,524 and 6,425,912 describe methods and devices for delivering RF energy to the skin using membrane structure. U.S. Pat. Nos. 6,453,202 and 6,425,912 describe a method and a device for delivering RF energy to the skin using dielectric electrodes. U.S. Pat. Nos. 6,381,498, 6,377,855, 5,919,219, 5,948,011 and 5,755,753 describe methods of collagen contraction using RF energy, and a reverse temperature gradient on the skin surface. U.S. Pat. Nos. 6,378,380, 6,377,854 and 5,660,836 describe methods of lypo-sculpturing using RF energy and external cooling to affect the collagen inside the adipose tissue.
Another method to reduce and redistribute adipose tissue is skin massaging. This method is based on improving of blood circulation and increasing fat metabolism. U.S. Pat. No. 6,662,054 describes a method for skin massaging in combination with non-aggressive RF heating for increasing skin and fat metabolism.
U.S. Pat. No. 6,273,884 discloses simultaneous application of optical energy and negative pressure to the skin in order to treat a skin defect. This method is limited by the light penetration depth, which does not exceed a 1-2 millimeters.
U.S. Pat. No. 5,143,063 describes a method based on thermal destruction of fat using the focusing of microwave or ultrasound energy in adipose tissue. But both types of energy are very expensive and its safety limitations are not clear.
The above cited methods and devices attempt to solve the problems created by excess adipose tissue such as body contouring, loose skin, and deep wrinkles, by contracting the superficial collagen tissue at a defined depth. These methods are limited in their penetration depth. A more effective and longer lasting result would be achieved by simultaneously heating the dermis and adipose tissue of the skin. However, in order to reach these layers, it is necessary to deliver RF current into the dermis and fat tissue to a depth of over 2 mm without damaging the skin.
Recently, a new RF system was introduced into the market by ALMA lasers Florida, USA. The system uses two different RF electrode configurations for RF energy delivery to the skin: a monopolar electrode configuration and a bipolar electrode configuration. A monopolar hand-piece is used for deep tissue heating of skin tissues while a different bipolar hand-piece is used for superficial heating of the skin. The disadvantages of using this method and system is that the two different hand-pieces (monopolar and bipolar) have to be separately used, increasing the complexity and cost of the system and doubling the time required for treatment of the same skin region resulting in increased cost of treatment. Additionally, a monopolar configuration for deep tissue heating is less beneficial because the current may typically find a flow path of low resistance where fat cells would not be directly affected.
An additional problem which is common to most RF treatments of skin fat is the electrode heating problem. The density of an RF current is always higher around the surface of the RF electrode applied to the skin surface. In order to avoid overheating the skin, various different methods for skin cooling may have to be applied. Cooling may be applied prior the RF energy application or/and simultaneously. However, the use of a skin cooling device in combination with RF energy delivery device increases the cost of the combined system and result in a cumbersome and more expensive unit. Moreover, cooling of the skin reduces the efficacy of the treatment resulting in more treatment sessions and longer treatment time.